X-ray shield structure for liquid cooled electron beam collectors and tubes using same



p 1970 L. H. SANDSTROM 3, 8

X-RAY SHIELD STRUCTURE FOR LIQUID COOLED ELECTRON BEAM CQLLECTQRS ANDTUBES USING SAME Filed May 20, 1968 INVENTOR. LARS H.5ANDSTROM @M l; Z

ATTORNEY United States Patent O 3,526,798 X-RAY SHIELD STRUCTURE FORLIQUID COOLED ELECTRON BEAM COLLECTORS AND TUBES USING SAME Lars H.Sandstrom, Cupertino, Califi, assignor to Varian Associates, Palo Alto,Calif., a corporation of California Filed May 20, 1968, Ser. No. 730,509Int. Cl. G21f 7/00; H01j 19/36 U.S. Cl. 313-22 1 8 Claims ABSTRACT OFTHE DISCLOSURE An electron beam tube is disclosed. The tube includes anelectron gun for forming and projecting a beam of electrons over anelongated beam path to a beam collector structure disposed at theterminal end of the beam. The beam collector structure includes achamber having an opening at one end for passage of the beam into thechamber and which is closed on the other end to collect that portion ofthe beam which passes through the chamber to the closed end. An array ofliquid coolant channels are provided along the side Walls of the beamcollector chamber in heat exchanging relation with the chamber walls forcooling same. A liquid coolant manifold structure is disposed over theclosed end of the collector for distributing to and collecting liquidcoolant from the array of coolant passageways. The liquid coolantmanifold includes first and second axially spaced chambers with a pairof pipes communicating with the first chamber and a pair of pipesinterconnecting the first and second chamber. An X-ray shield as of leadis provided closely surrounding the beam collector chamber and theliquid coolant channels, such shield also covering over the end of thecoolant manifold and including a portion disposed intermediate the firstand second axially spaced chambers thereof. The coolant pipes connectedinto the first chamber and interconnecting the first and second chambersof the manifold are axially offset with respect to each other such thatthe X-ray shield portion disposed between the two chambers blocks anyline of sight passageway for X-rays from the beam collector chamberthrough the two sets of pipes. In the preferred embodiment, a pair ofelbow-shaped X- ray shield members are provided covering elbow pipefittings connecting into the first manifold chamber.

DESCRIPTION OF THE PRIOR ART Heretofore, electron beam tubes haveincluded collector structures having an X-ray shield for preventingescape of X-rays from the collector. Typical of such prior art X-rayshields is that disclosed in U.S. Pat. 3,374,390 issued Mar. 19, 1968and assigned to the same assignee as the present invention. In thatprior tube structure, the beam collector chamber is surrounded by anelongated cup-shaped X-ray shield, as of lead. The bottom of thecup-shaped lead shield member is apertured to accommodate passage of apair of pipes for conducting liquid coolant to and from a coolantmanifold structure afiixed over the end of the beam collector chamber.

The problem with such an X-ray shield structure is that X-rays,generated within the beam collector chamber, can pass out of the X-rayshield by passing through the apertures in the shield which wereprovided to accommodate Patented Sept. 1, 1970 the liquid coolant pipes.When the electron tubes are operating at relatively high beam voltagesand high power levels, the X-ray radiation escaping from the beamcollector through the apertures provided for the coolant pipes becomessubstantial and constitutes a radiation hazard to operating personnel.Previous attempts to solve the escape of radiation from theaforementioned tube structure have included the provision of additionalX-ray shielding members, such as sheets of lead, wrapped around and overthe coolant pipes leading to and from the beam collector structure.While such additional shielding members can substantially reduce thedangerous X-ray radiation such members become excessively large andbulky because they are disposed at some distance from the collectorstructure.

Therefore, a need exists for an improved X-ray shielding structure thatmay be incorporated as an integral unit into the beam collectorstructure, thereby reducing the size and weight of the required X-Iayshielding members.

SUMMARY OF THE PRESENT INVENTION The principal object of the presentinvention is the provision of an improved X-ray shield for liquid cooledelectron beam collectors and tubes using same.

One feature of the present invention is the provision, in a liquidcooled electron beam collector structure, of separating the liquidcoolant manifold structure into a pair of axially spaced coolantchambers disposed at the end of the beam collector and offsetting theaxial centerlines of one pair of coolant pipes, communicating With theouter chamber, with respect to the axial centerlines of a second pair ofcoolant pipes communicating through the axial space between the axiallyspaced chambers, and disposing an X-ray shield structure with a firstportion in the space betweent he two axially spaced chambers and asecond portion over the outer end of the manifold to block a line ofsight path for the X-rays from the inside of the beam collector to theoutside thereof through the liquid coolant manifold structure.

Another feature of the present invention is the same as the precedingfeature wherein the X-ray shield structure disposed between the twoaxially spaced chambers is apertured to accommodate the pipescommunicating therebetween and is split axially and transversely thereofalong a line intersecting with the apertured portion to facilitateplacement of the X-ray shield around the liquid passageways.

Another feature of the present invention is the same as any one or moreof the preceding features wherein the end portion of the X-ray shieldstructure, which covers over the liquid coolant manifold, includes oneor more apertures to accommodate the liquid passageways communicatingwith the manifold and such end covering shield structure being axiallysplit along a transverse line intersecting with the apertured portion ofthe structure to facilitate placement of the X-ray shield structurearound the liquid passageways.

Another feature of the present invention is the same as any one or moreof the preceding features wherein the liquid passageways communicatingwith the fluid manifold structure include a pair of elbow pipe fittingsand a pair of elbow-shaped X-ray shield structures being fitted oversaid elbow pipe fittings to further reduce the possibility of strayX-ray radiation leaking through the X-ray shield structure.

Another feature of the present invention is the same as any one or moreof the preceding features wherein the outer end manifold chamberincludes a partitioning wall partitioning the chamber into two lesserchambers for passage of liquid coolant in opposite directions throughthe partitioned chamber.

Other features and advantages of the present invention will becomeapparent upon a perusal of the following specification taken inconnection with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal view, partlyin section, of an electron beam tube incorporating features of thepresent invention,

FIG. 2 is an enlarged longitudinal sectional view of a portion of thestructure of FIG. 1 delineated by line 22,

FIG. 3 is a schematic line diagram of a transverse sectional view of thestructure of FIG. 2 taken along lines 3-6 in the direction of thearrows, and

FIG. 4 is a sectional view of a portion of the structure of FIG. 3 takenalong the lines 4-4 in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, thereis shown an electron beam tube 1 incorporating features of the presentinvention. The tube 1 includes an electron gun 2 for forming andprojecting a beam of electrons 3 over an elongated beam path to a beamcollector structure 4 disposed at the terminal end of the beam path. Anelectromagnetic interaction circuit 5 is disposed intermediate the gun 2and collector 4 and along the beam path 3 for electromagneticinteraction with the beam to produce an output microwave signal.

Input microwave signals to be amplified are applied to the upstream endof the interaction circuit 5 via an input coaxial line 6. Outputmicrowave energy is extracted from the downstream end of the microwavecircuit 5 via output waveguide 7 which is sealed in a vacuum tightmanner by means of a wave permeable dielectric window member 8. A beamfocus solenoid 9 coaxially surrounds the tube 1 for producing an axiallydirected beam focus magnetic field over the beam path for confining thebeam to a desired beam diameter throughout the interaction circuit 5.Inside the collector structure 4 the beam spreads due to space chargedebunching forces and is collected more or less uniformly over theinterior surfaces of the collector, more fully described below withregard to FIGS. 2-4. The aforedescribed tube structure is essentiallysimilar to that described and claimed in the aforecited US. Pat.3,374,390.

Referring now to FIGS. 2 and 3, there is shown the beam collectorstructure 4 incorporating features of the present invention. Morespecifically, the collector structure 4 includes a hollow conductivechamber 11 as of copper which is open at one end 12 for passage of theelectron beam 3 into the collector chamber 11. The other end of thechamber 11 is closed by a conical end wall 13- for collecting thatportion of the beam which passes through the beam collector chamber 11to the wall 13. The external side surfaces of the beam collector chamber11 include an array of closely spaced longitudinally directed fins 14 asof copper. The spaces between adjacent fins 14 constitute liquid coolantpassageways which extend substantially the full length of the collectorchamber 11. A radial array of fins 14 extend radially from the center ofthe end wall 13 to the outer diameter of the chamber. The radiallydirected fins 14 define liquid coolant passageways therebetween on theoutside of the conical end wall 13. The radial passageways communicateonly with alternate ones of the passageways along the side walls of thechamber.

A cylindrical baffle 15, as of stainless steel, surrounds and is aifixedover the outer side edges of the vanes 14 1 to define the outer sidewall of the coolant passageways. The bafile 15 is sealed at its upstreamend to a shoulder portion 16 of the beam collector structure 4. A hollowtoroidal shaped coolant collecting chamber 17 is defined by the spacesbetween the upstream ends of the fins 14 and the inside surface of theshoulder 16. A conically shaped bafile plate 18, as of stainless steel,is affixedover the conical array of coolant fins 14 and passagewaysprovided of slots and thence along the sides of the collector to thetoroidal collecting chamber 17 from whence the coolant passes in areverse direction along the outside of the collector chamber 11 in theadjacent set of slots through the slotted peripheral margins of thebafiie 18 into an annular collecting chamber .20 of a coolantdistribution manifold structure 21 disposed over the outer end of thecollector chamber 11.

In the coolant distribution manifold structure 21., the.

structure is divided into a pair of axially spaced chambers, i.e.,annular collection chamber 20 and an outer axially spaced shallowcylindrical chamber 22. Chambers 20 and 22 are defined by the regions ofspace between transverse disc structures 23, 24, 25 and the outersurface of the conical baffie 18. More specifically, end chamber 22 isdefined by the region of space between the end disc-shaped wall 23 andtransverse disc 24, whereas collector chamber 20* is defined by thespace between the conical bafiie 1'8 and the disc 25. The side walls ofthe chambers 20 and 22, respectively, are defined lby cylindricalsections of the cylindrical bafile 15. A pair of cylindrical coolantpipes 26 and 27 interconnect chambers 22 i with the collection chamber20 and with the conical array of radially directed coolant channels onthe end of the collector wall 13, respectively. The coolant pipes 26 and27 pass through the axial space 28 between the collec-v tion chamber 20and the outer chamber 22.

An apertured disc-shaped X-ray shield member 29, as

of "/2 inch thick lead, is disposed in the region 28 between thecollection chamber 20 and the end chamber 22. The lead shield member 29includes a pair of apertures 31 and 32, respectively (see FIG. 3) toaccommodate the coolant pipes 27 and 26, respectively. The,

X-ray shield disc 29 is axially split along a transverse line 33 whichintersects both apertures 31- land 32 to divide the disc-shaped shieldmember 29 into two parts to facilitate placement of the shield 29 in thespace 28,- since by splitting the member 29 it may be slipped into theregion 28 from diametrically opposed sides as in dicated by the arrows34 in FIG. 3. A similarly discshaped lead shielding member 35 is affixed.over the outer end of the coolant distribution manifold 21 and issimilarly apertured by a pair of holes 36 and 37 to a accommodate a pairof elbow pipe fittings 38 which are in fluid communication with the endchamber 22 via a pair of ports 39 provided in the end wall 23. The ports39,

elbow fittings 38, and the corresponding apertures 36 i and 37 in thelead shielding member 35 are axially oifset.

with respect to the axes of the coolant pipes 26 and 27 which passthrough the first X-ray shielding disc 29. In

this manner, X-rays generated within the collector chamber 11 andtending to pass in straight line out through i the end of the collectorstructure are blocked due to the lack of a straight linepassageway'through bothof the first and second pairs of holes in theX-ray shields 31 and 32 and 36 and 37, respectively. The end X-rayshielding disc 35 is axially split by means of a transverse joint 41which intersects both apertures 36 and 37 such that the end shield 35may he slipped into position around the elbows 38 from diametricallyopposed sides as in dicated by arrows 42.

One elbow-shaped lead shield member 43 is aflixed over the pair of elbowfittings 38 to further block the escape of X-rays that may possibly findan off axis straight line path through aperture 32 in shield member 29and through either aperture 36 or 37 in shield member 35.

The transverse joints 33 and 41 in X-ray shielding disc members 29 and35 include an axially offset region as shown in FIG. 4, such that X-rayscannot pass axially through the joints.

The end chamber 22 in the coolant distribution manifold includes aninternal partition 44 which has a right angle bend as shown in FIG. 3 toseparate the chamber 22 into two separate portions to accommodate theinflow of cold coolant and the outflow of warm exhaust coolant. Thedirection of coolant flow is indicated by the arrows of FIG. 3 and,briefly, input coolant flows through input elbow pipe fitting 38 throughport 39 thence through the centrally disposed coolant pipe 26 into thecenter of the conical array of cooling fins provided on the end of thecollector. The coolant then flows radially across the end of thecollector and down the sides returning through adjacent channels in thesides and into the collector chamber 20. From the collector chamber 20,the coolant flows through pipe 27 into the exhaust side of thepartitioned chamber 22 and thence through the exhaust elbow fitting 38which communicates through the shield aperture 36 with the chamber 22.

A cylindrical X-ray shielding member 45 surrounds the sides of thecollector chamber 11 and the distribution manifold 22 to prevent theescape of X-rays out the sides of the collector. A magnetic shieldingcup-shaped member 46 as of iron surrounds the X-ray shielding members I45 and 35, respectively. In certain tube embodiments, it

is desirable to have the collector 4 operating at a potentialindependent of the potential applied to the body of the tube such thatbody current can be monitored independently of the current collected bythe collector 4. In such a case, conventional insulator structures, notshown, support the collector chamber 11 from the body of the tube.However, the outer X-ray shield structure 35, 45, and 43 and themagnetic shield member 46 are typically operated at body potential and,therefore, an insulator must be provided between the external X-rayshielding members 35, 45 and 43 and those internal portions of thecollector structure to be operated at the independent potential.Accordingly, a thin cup-shaped insulator 47 as of sheet Teflon, isaflixed over the end of the coolant dis tribution manifold structure 21and an elbow-shaped insulator 48 is disposed between the elbow X-rayshielding members 43 and the elbow pipe fittings 38. Insulative hoses,as of rubber, are then utilized for connecting the elbow fittings 38 tosuitable pipes for piping a liquid coolant to and from the collectorstructure 4.

The advantage of the X-ray shield structure of the present invention isthat the pair of axially spaced discshaped X-ray shielding members 29and 35, having offset apertures therein to accommodate the flow ofcoolant through the coolant manifold structure, effectively blocks allX-ray emission from the collector which tends to pass out the endthereof. The cylindrical X-ray shielding member 45, which surrounds theside of the collector chamber 11, and the sides of the distributionmanifold 21 effectively blocks all X-ray radiation which tends to passout through the sides of the collector 4. Thus, an efficient and compactX-ray shield structure for beam collector structures is obtained.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In an electron tube apparatus, means for forming and projecting abeam of electrons over an elongated beam path, means at the terminal endof the beam path for collecting and dissipating energy of the beam, saidbeam collecting means including a chamber having an opening in one endfor passage of the beam into said chamber and being closed on the otherend to collect that portion of the beam passing through said chamber tothe closed end thereof, means forming liquid coolant passageways forpassing a liquid coolant along the side walls of said beam collectorchamber in heat exchanging relation with the walls of said chamber forcooling same, means forming a liquid coolant manifold structure disposedover the closed end of said beam collector chamber for distributing andcollecting the liquid coolant through said liquid coolant passageways,means form ing an X-ray shield structure disposed closely surroundingsaid collector chamber and liquid coolant passageways and having aportion covering the end of said beam collector chamber and said liquidcoolant manifold, the improvement wherein, said liquid coolant manifoldstructure comprises first and second axially spaced chambers, said firstchamber having a pair of fluid passageways communicating therewiththrough said end covering portion of said X-ray shield, means forming asecond pair of liquid passageways communicating between said first andsecond axially spaced chambers of said manifold, said first and secondpairs of fluid passageways being disposed in axially offset relationwith respect to each other such as to block an axially directed straightline passageway through both of said first and second pairs ofpassageways, and an X-ray shield structure disposed in the axial spacebetween said first and second manifold chambers for blocking passage ofX-rays except through said liquid passageways communicating between saidaxially spaced chambers.

2. The apparatus of claim 1 wherein said X-ray shield structure disposedin the space between said first and second manifold chambers comprises astructure apertured to accommodate said pair of fluid passagewayscommunicating between said first and second manifold chambers, and saidapertured structure being axially split along a transverse lineintersecting said apertured portion of said structure to facilitateplacement of said X-ray shield structure around said liquid passageways.

3. The apparatus of claim 2 wherein said apertured X-ray shieldstructure includes two apertures, and said structure is axially splitalong the transverse line intersecting both of said apertures in saidstructure.

4. The apparatus of claim 2 wherein said apertured X-ray shieldstructure is disc-shaped.

5. The apparatus of claim 1 wherein said end portion of said X-rayshield structure which covers over said liquid coolant manifold includesan apertured structure to accommodate said liquid passagewayscommunicating with said liquid manifold chamber through said end portionof said X-ray shield structure, said end covering shield portion beingaxially split along a transverse line intersecting with said aperturedportion of said end portion to facilitate placement of said X-ray shieldstructure around said liquid passageways.

6. The apparatus of claim 5 wherein said end covering X-ray shieldportion includes two apertures, and said portion is axially split alonga transverse line intersecting both of said apertures in said endportion.

7. The apparatus of claim 5 wherein said liquid passagewayscommunicating with said first chamber are defined by a pair of elbowpipe fittings and a pair of elbowshaped X-ray shield structures beingfitted over said elbow pipe fittings.

7 8 8. The apparatus of claim 1 wherein said first mani- 3,122,6692/1964 Nelson 313*24 fold chamber includes a partitioning wallpartitioning 3,305,742 2/1967 McCune 313--21 X said chamber into twolesser chambers for passage of 3,359,451 12/1967 Zitelli et a1 31330 Xliquid coolant in opposite directions through said parti i d h b 5 JAMESW. LAWRENCE, Primary Examiner References Cited E. R. LA ROCHE, AssistantExaminer UNITED STATES PATENTS US. Cl. X.R.

3,098,165 7/1963 Zitelli 313-32 X 313-32, 35; 315-5.38;250-108 3,104,3389/1963 Symons 3l55.38 X 10

